Stainless and carbon steel in concrete

[bagnamento]

I'm reviewing a project which includes fillet welding of two plates made of carbon steel and stainless steel (Type 304).
The joint will not be loaded (it's a seal joint). It will be exposed to air first and then completely immersed in concrete.
Is this environment harmful to a c-steel/stainless steel joint?
Would it be enough, maybe not even necessary, to paint both plates after welding?
Is it necessary to change materials to stainless steel only?
Thanx

 

[Goahead]

Carbon steel should be buttered with 309 or 312 stainless before welding to 304 with 347 filler metal.
304L should be preferred to 304 to avoid sensitization (susceptibilty to corrosion as a consequence of precipitation of chromium carbides).

http://www.welding-advisers.com/

 

[EdStainless]

Is there any chance of this joint ever seeing any water?

The concern about sensitization of the stainless is not only will it corrode more rapidly but there is also a greater chance for cracking.
I have seen CS to SS seals made using a narrow strip of 309 welded to each side. You could use 309 filler for both welds.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[bagnamento]

EdStainless,
no, the joint will never see water.